Dark matter constraints on gaugino/Higgsino masses in split supersymmetry and their implications at colliders

In split supersymmetry, gauginos and Higgsinos are the only supersymmetric particles that are potentially accessible at soon-to-be-completed colliders. While direct experimental research, such as the LEP and Tevatron experiments, have given robust lower bounds on the masses of these particles, cosmic dark matter can give some upper bounds and thus have important implications for research at future colliders. In this work we scrutinize such dark matter constraints and show the allowed mass range for charginos and neutralinos (the mass eigenstates of gauginos and Higgsinos). We find that the lightest chargino must be lighter than about 1 TeV under the popular assumption M₁=M₂/2 and about 2 or 3 TeV in other cases. The corresponding production rates of the lightest chargino at the CERN large hadron collider (LHC) and the International Linear Collider (ILC) are also given. While in some parts of the allowed region the chargino pair production rate can be larger than 1 pb at the LHC and 100 fb at the ILC, other parts of the region correspond to very small production rates, and thus there is no guarantee of finding the charginos of split supersymmetry at future colliders. PACS 14.80.Ly, 95.35.+d